The use of turbocharged engines is a common practice. The turbocharger increases the quantity of air for combustion and increases the heat value or temperature of the intake air. To compensate for the increased temperature of the intake air, an aftercooler is used to reduce the temperature of the compressed intake air. Many of the cooling systems include a water jacket aftercooler. In the water jacket aftercooler a coolant from the engine is circulated through the aftercooler and the intake air is cooled. The use of engine coolant limits the temperature to which the intake air can be cooled. More recently, the cooling medium of the aftercooler has been converted to use ambient air and an air to air aftercooler has replaced the water jacket aftercooler. In some applications and under some operating conditions, the air to air aftercooler reduces the temperature of the intake air too much. Since ambient air is used as the coolant or recipient fluid, the temperature, pressure and humidity of the ambient air varies depending on geographic location and season. Thus, the temperature and humidity of the intake air varies accordingly. And, with the advent of exhaust gas recirculation to further reduce emissions, the mixture of the intake air with a varying humidity content and the exhaust gas to be recirculated has been found to form sulfuric acid which is detrimental to the engine. Under these varying conditions the combustion of the intake air and fuel results in varying characteristics. Under certain conditions the emissions therefrom can be increased due to the combustion temperature having the characteristic for forming excess hydrocarbons and other emissions. And, under other conditions, the structure of the engine can be damaged due to excessive power being developed. Thus, a system for controlling the temperature of the intake air is needed.
The present invention is directed to overcome one or more of the problems as set forth above.